President Donald Trump’s bid to cut off birthright citizenship is a “flagrantly unlawful attempt to strip hundreds of thousands American-born children of their citizenship based on their parentage,” attorneys for 15 states and the city of San Francisco said Tuesday in a lawsuit challenging the president’s executive order signed just hours after he was sworn in Monday.

The lawsuit accused Trump of seeking eliminate a “well-established and longstanding Constitutional principle” by executive fiat.

“The President has no authority to rewrite or nullify a constitutional amendment or duly enacted statute. Nor is he empowered by any other source of law to limit who receives United States citizenship at birth,” the lawsuit said.

Trump’s order directed federal agencies — starting next month — to stop issuing citizenship documents to U.S.-born children of undocumented mothers or mothers in the country on temporary visas, if the father is not a U.S. citizen or permanent resident.

According to the lawsuit, about 150,000 children born each year to two parents who were noncitizens and lacked legal status could lose access to basic health care, foster care, and early interventions for infants, toddlers, and students with disabilities.

“They will all be deportable, and many will be stateless,” the lawsuit said.

The states warned the executive order would also cause them to lose federal funding for programs that render services to children regardless of their immigration status.

While Trump’s order purports to unilaterally end birthright citizenship, only the U.S. Supreme Court can determine how the 14th Amendment applies.

“President Trump’s attempt to unilaterally end birthright citizenship is a flagrant violation of our Constitution,” said New Jersey Attorney General Matthew Platkin. “For more than 150 years, our country has followed the same basic rule: babies who are born in this country are American citizens.

The states are seeking to invalidate the executive order and stop any actions taken to implement it. Their lawsuit requests a preliminary injunction to immediately prevent the order from taking effect.

“The great promise of our nation is that everyone born here is a citizen of the United States, able to achieve the American dream,” said New York Attorney General Letitia James. “This fundamental right to birthright citizenship, rooted in the 14th Amendment and born from the ashes of slavery, is a cornerstone of our nation’s commitment to justice.”

On Tuesday, nonprofit groups in Massachusetts and New Hampshire also filed federal lawsuits challenging Trump’s birthright citizenship executive order.